This one was surprisingly quick, think I've spent about 5 hours and its 80% done. I need to do the Georgia area, and the area east of the Don as these were not covered in the source map I raided. The main challenge was projection. I used a google maps screen shot Pete provided as my base map for getting things in the right place, but given the size of the earth being mapped this leads to some distortion. All maps project a spherical bumpy world on to a 2 dimension flat surface, as such you cannot keep all things in perfect proportion. My map distorts the coast a bit different to say Mark Simonitch's map for the up coming Stalingrad 44 game. Most things look pretty good but If you measured the exact distance between the Don and Volga it might be a little too close together in the north compared with the south. Fortunately most gamers never notice these things as long as it sort of looks ok.
I've gone for a white background to evoke snow, even though most of the campaign is in the autumn/summer, and I've paired it with a deep blue for the waters as it gives a clean visual contrast. In general it looks like a mid 80s style map.
If you are in the UK and want to play a 40 player + simulation of the Case Blue campaign check out Pennine mega games; http://www.penninemegagames.co.uk/case-blue-42.html